P501: CLI120-001 PHASE1B DOSE ESCALATION STUDY OF RVU120 IN PATIENTS WITH AML OR HIGH RISK MDS SAFETY AND EFFICACY DATA UPDATE
Authors: C. Abboud, Z. Jan Maciej, G. Borthakur, S. Solomon, B. Howard, T. Bradley, E. Mouhayar, N. Angelosanto, H. Nogai, A. Glasmacher, R. Dudziak, K. Brzozka, T. Rzymski, P. Littlewood, E.-L. Maranda
Journal: HemaSphere (2022)

Background: CDK8 and its paralog CDK19 have central roles in maintenance of cancer cell viability and undifferentiated state for a variety of tumor types. (Dannappel et al. 2019; Rzymski et al. 2015; Philip et al. 2018). RVU120 (SEL120), a novel CDK8/CDK19 kinase inhibitor with significant efficacy in preclinical AML models, has shown clinical efficacy in a currently ongoing phase Ib trial in patients with relapsed/refractory (R/R) AML or HR-MDS (NCT04021368). This paper provides update with new available data on disease evaluation from ongoing patients and further enrolment into next cohort level 85 mg. Aims: The primary objective of the study is to determine preliminary safety profile, dose limiting toxicities (DLTs), maximum tolerated dose (MTD) and the recommended phase 2 dose of RVU120 as a single agent. Secondary objectives include PK, antileukemic activity and exploratory PD characterization. Methods: The study comprises at least 7 dose escalating cohorts. The first 3 cohorts followed an accelerated scheme, 1 patient enrolled/cohort from 10 to 50 mg dose levels, from cohort 4 (75 mg) to 7 (100 mg) doses onwards a 3 + 3 design is followed. Data from each cohort is evaluated by a data review committee (DRC). RVU120 is administered orally every other day, for a total of 7 doses, in a 3-week treatment cycle until disease progression/unacceptable toxicity. Adverse events are graded according to NCI-CTCAE v.5.0. DLTs are assessed at completion of C1. Disease evaluation is performed according to Dohner 2017 and Cheson 2006 response criteria for AML and MDS respectively. PK parameters are calculated by non-compartmental analysis. Pharmacodynamic (PD) activity is assessed by flow cytometry measure of pSTAT5 Ser725 levels, that are highly dependent on the activity of CDK8 and CDK19 in AML/MDS cells. Results: At data cut off of 23rd Feb22, 13 pts have been enrolled, median age 73 years and median 2 previous lines of therapy, ECOG PS 2 in 4 pts, 1 in 7, 0 in 2. No DLTs were observed, all 14 Serious Adverse Events, including 1 COVID19 death and 1 pancreatitis, were not related to study drug (G1 fever, G2 Upper Respiratory Infection, G3: pseudomonas sepsis; urinary tract infection; febrile neutropenia; lung infection, pain, hemoptysis, pleural effusion, G5 pneumonitis, death NOS, pancreatitis). Cohort 1 pt, 10 mg dose level, and cohort 2 pt, 25 mg, showed stable (SD) and progressive disease (PD) respectively at the end of C1. Cohort 3 pt, an 81 YO male HR-MDS, escalated from 50 to 75 mg dose from C7, is SD at C24D13 with Erythroid Hematological Improvement on C5, C7, C10, C18. Cohort 4, 75 mg dose pt, a 62 YO male with AML DNMT3A pos, relapsing after Ven/Dec, achieved CRi at the end of C1 and CR in C7, and progressed at the end of C8. Two out of the remaining 4 pts treated at 75 mg reached SD (1 still ongoing at C3D15 and another died on C3D20 while on SD), 1 pt died of COVID-19 pneumonitis on C1D18, 1 pt with AML secondary to MPN was SD at C2 and progressed on C4. Two pt were treated at 110 mg (cohort 5), 1 not evaluable died for pancreatitis and 1 was SD at the end of C1. 2 pt entered cohort 6, 85 mg, and will be evaluable at the end of March 2022. Summary/Conclusion: Preliminary results from the first 6 cohorts have shown a favorable safety and a predictable PK profile of RVU120. Meaningful PD activity and clinical efficacy were observed at 50 and 75 mg doses. Enrollment is currently ongoing at 85 mg cohort